High frequency power supply circuit



April 1937- L. D. MILES 2,078,151

HIGH FREQUENCY POWER SUPPLY CIRCUIT Filed April 16, 1936. 2 Sheets-Sheet l Inventor: Lawrence D. Miles,

l-hs Attorney.

April 29, 193'?! n... D. MELES p fi HIGH FREQUENCY POWER SUPPLY CIRCUIT Filed April 16, 1936 2 Sheets$heet 2 IO'I . lnverfcor: Lawrence D. Miles,

A bha I Patented Apr. 20,- 1937 PATENT; OFFICE men FREQUENCY PowER. SUPPLY cmcorr Lawrence D. Miles, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application April 16, 1936, Serial No. 14,646

9 Claims.

My invention relates to electric systems for the generation of high frequency power, particularly for industrial use, from commercial low voltage continuous current sources and low frequency alternating current sources, and its object is to provide electric systems for the above mentioned and similar purposes which are characterized by low initial and operating costs, in addition to simplicity, efllciency, reliability and small space and weight requirements.

It is recognized that in theuse of alternating electric power in industrial applications an optimum frequency exists for performing a given operation. For example, 360 cycle power is commonly used to bake enamel on automobile fenders; 1,000 to 2,000 cycle for metal and scrap melting; 900 to 2,000 cycle power for certain alloying processes; 4,800 cycle power in the manufacture of razor blade steel; 5,000 cycle power in ozone generation; 30,000 cycle power'for certain pipe welding processes; 40,000 to 50,000 cycle power in small induction furnaces; and 50,000 cycle power in sterilizing milk.

Various types of apparatus have been proposed and used for providing high frequency power, among which are equipment including rotating electric machines, equipment including high vacuum discharge devices or tubes, and equipment includingvapor electric or gaseous discharges or tubes.

Difficulties have been encountered, however, in certain cases in the pplication of these and other types of appara o the supply of kilocycle frequency power n any of the above cited systems used heretofore for the supply of high frequency power, requirements in the matter of operating costs, emciency and life have been reasonably well met in general but the principal difficulty encountered in their application to general industrial uses has been relatively high initial cost.

In accordance with my present invention I have obviated the above' mentioned and other difficulties attendant on the supply of high frequency power, by the provision of novel electric circuit arrangements which employ the arc tube as an element in the source of high frequency power. The are tube consists essentially of two electrodes closely spaced in inert gas, preferably hydrogen, under relatively high pressure. In this tube an optimum gas pressure may beused to give optimum power, the electrodesmay be spaced permanently for maximum efficiency at rated output, and oxygen and water vapor may be driven from the tube before inert gas is admitted,

.thus insuringuniform power, high efflciency and long life. The optimum circuit arrangement for any given installation depends on the type of load, the wave shape and the frequency desired. Besides the arc tubes, essential equipment comprises choke coils and resistors, or both, in the direct current or commercial alternating current single phase or polyphase supply circuits, and capacitors and inductors associated with the arc tubes in high frequency oscillating tube circuits. Output at the desired voltage is usually taken from secondaries of transformers constituting inductors, orin certain cases, as in induction furnace heating, output is taken directly from the inductors which then constitute the furnace coils.

My invention will be better understood from the following description when considered in connection with the accompanying drawings and its scope will be pointed out in the appended claims.

Referring to the drawings, Fig. 1 is a diagrammatic representation of a highfrequency power system, including a single arc tube, in which my invention has been embodied; Fig. 2 shows curves illustrating the operation of the system shown in Fig. 1; Fig. 3 is a diagrammatic representation of a high frequency power system embodying my invention, including preferably two double-electrode arc tubes; Fig. 4 represents diagrammatically a high frequency power system embodying my invention, having a multiphase input and a plurality of outputs; Fig. 5 represents a system embodying my invention, similar to that of Fig. 4 but having a single output; Fig. 6 shows curves illustrating the operation of the systems of Figs. 4 and 5; Fig. '7 represents diagrammatically a high frequency power system embodying my invention, similar to that shown in Fig. 5 but including a phasing means in the oscillation circuits; Fig. 8 illustrates a different means in accordance with my invention for taking the output from the circuit shown in Fig. 7; and Fig. 9 represents diagrammatically a high frequency -,,power system in accordance with my invention including a starting circuit for the arc tube.

In. Fig. 1, numeral l designates a direct current input circuit which may be, for example, of commercial low voltage, or an alternating current circuit such as a usual low voltage commercial frequency single-phase power circuit. The input cincuit I0 is connected to a high fre= quency oscillation circuit ll through an inductance or choke coil l2 and an arc-tube l3 including twosimilar closely spacedelectrodes It, l in a relatively high pressure hydrogen atmosphere and enclosed in a glass tube [6. The oscilmien circuit u, in series with tube I3, includes in series a transformer I1, constituting an induc tor element, and a capacitor I8. The numeral I8 designates an output circuit for the high frequency power, connected to the secondary 28 of the transformer I1.

In Figure 3, numeral 2| designates a direct current or an alternating current input circuit as in Fig. 1. Input circuit 2| is connected to a high frequency oscillation circuit 22 including in series two arc-tubes 23, 24, a transformer 25 constituting an-inductor, and a capacitance 28. One side of the input circuit 2| is connected as through an inductance or choke coil 21 and'the common connection of the tubes to an electrode, 28, 28, of each of the tubes. The other side of the input circuit 2| is connected through one section 38 of a resistor 3| to the inductor 25 and the other electrode 32 of tube 23, and through'the other section 33 of the resistor 3| to thecapacitor 28 and the other electrode 34 of the other tube 24. A high frequency output circuit 35 is connected to the secondary 38, of the transformer or inductor 25. Instead of the two double-electrode tubes 23, 24, one three-electrode tube, having a common electrode connected to the choke 21 and two other electrodes corresponding respectively to electrodes 32, 34 may be used.

In Fig. 4, numeral 31 designates a three-phase alternating current circuit of commercial low frequency the three phases 38, 38, 48 of which are connected respectively through resistors 4 I, 42, 43 to series high frequency oscillation circuits 44, 48, 48 including respectively one of the arc tubes 41, 48, 48, each of which includes a pair of electrodes 58 and 5|, one of the transformers 82, 83, 54 constituting inductors, and one of the capacitors 55, 58, 51. One of the electrodes, as 58, of each tube is connected to a different one of the phases 38 to 48 and the other electrode, 5|, of each tube is connected, as by a common lead 58 and ground, to the neutral point 58 of the three-phase supply circuit 31. Three separate high frequency output circuits 88, 8|, 82 are provided connected respectively to the secondaries 83, 84, of the transformers or inductors-52, 53, 54.

In Fig. 5, the circuit arrangement is similar to that of Fig. 4 in that the phases 38, 38, 48 of the ee phase alternating current supply circuit 31 are connected respectively through resistors 4I, 42, 43 to series high frequency oscillation circuits which are designated in Fig. 5 by-the numerals 88, 81, 88.. The latter oscillation circuits include respectively one of the arc-tubes 41, 48, 48 and'one of the capacitors 55, 58, 51, but in Fig. 5 the three oscillation circuits include a common inductor element constituted by the transformer 88, and in Fig. 5 a single output circuit 18 is provided connected to the secondary 1| of transformer 88.

In the embodiments of my invention shown in Figs. 4 and 5, the pairs of electrodes 58, 5| of the arc-tubes 41 to 48 are preferably so arranged that the electrode spacing is relatively great, for a purpose to be explained hereinafter.

In Fig. 7, the circuit arrangement is similar to that illustrated in Fig; 5, a three phase alternating current circuit 31 supplying, from its phases 38 to 48 and through resistors 4| to 43,

three high frequency oscillation circuits 12 to 14,

the secondary 83 of the transformer. In Fig. 7, however, the spacing of the electrode pairs 84, 84a is not relatively great, and further, in order to produce in the high frequency output circuit 82 overlapping oscillations of the desired and established frequency and phase, a phasing transformer 85 is provided in the oscillation circuits 12 to 14, the phasing transformer comprising a three-legged core 85a and phase windings 88 to 88 connected respectively in series in the oscillation circuits 12 to 14. Instead of the output circuit 82, connected to a secondary winding of the inductor element 8|, the output circuit 88 may be provided as shown in Fig. 8 wherein the circuit 88 is connected to a winding 88 on a fourth leg 8| of the phasing transformer 85 of Fig. '7.

It will be understood that in the forms of the invention illustrated in the circuit arrangements of Figs. 1, 3, 4, 5, and '1, suitable means (not shown) for facilitating the initiation of the oscillatory current flow through the arc tubes may be provided.

In Fig. 9, thenumeral 82 designates a direct current or alternating current input circuit as in Figs. 1 and 3. Input circuit .82 is connected through a line switch 83, an inductance element or choke coil 84 and a resistor 85 to a high frequency oscillation circuit 88 comprising in series an arc tube 81, a capacitor 88, and a transformer 88 constituting an inductor element. One side of the input circuit 82 is connected to the capacitor 88 and one of the electrodes, as I88, of

the arc-tube and the other side of the input I circuit is connected to the transformer 88 and the other electrode |8I of the arc-tube. An

output circuit I82 is connected to the secondary side of the supply circuit 82, and the resistor I81 is adapted to be connected across the circuit 82 bya switch I88, preferably through the heater element I88 for the thermostatic device I85, whereby the one switch I88 controls the operation of the heater element I88 and also the connection of the resistance element I81 in the auxiliary electrode circuit. Preferably the common point of connection of resistor I81 and heater I88 is at the end II8 of movable thermostatic element I85 oppositeto the end of the latter element to which the auxiliary electrode I84 is connected.

In operation of the system shown in Fig. 1, assuming that input circuit I8 is a circuit of commercial low voltage alternating current, the voltage wave of the supply circuit I8 is as shown by curve III of Fig. 2. At each half wave of the supply voltage the tube becomes conducting when the breakdown voltage is reached. Oscillations, indicated generally by the curve II2 of Fig. 2, are thereupon set up in the high frequency oscillation circuit II and are induced in the output circuit I8. The tube I3 conducts current alternately in one direction and the other as the tube breakdown voltage is reached .at each half wave of the supply voltage. Since power from the input circuit I continues to be supplied during each half wave to the oscillation circuit II as long as the voltage in the supply circuit reaches the breakdown voltage of the tube, the output oscillations during this portion of the half waves are substantially undamped as shown in Fig. 2. In case the input I0 is a direct current circuit, 'the tube conducts current, as the breakdown voltage is reached; and supplies power to the oscillating circuit II, in which a continuous train of high frequency oscillations is produced.

Inoperation of the system shown in Fig. 3,.

assuming that supply circuit 2I is a' commercial low voltage direct current circuit, when voltage is'applied to the tubes 23, 24,- one of the tubes,

as tube 23, breaks down and. capacitor 26 is charged to sufilcient voltage to cause breakdown of the other tube, 24. Capacitor 26 then discharges through the oscillating circuit 22. At the instant that capacitor is completely discharged, a high current is flowing in the circuit 22. The inductor 25 continues this current flow which over-discharges capacitor 25 and drives the voltage of tubes 23, 24 negative, whereupon the arcs extinguish and the tubes are again on open circuit. The tube 23 then again breaks down,'the capacitor 26 is charged and the tube 24 breaks down. The above cycle is repeated to produce high ,frequency power in circuit 22,

and this power is induced in 'the output circuit 35., In case the input 2| is a commercial low voltage lowirequency alternating current circuit, the operation is essentially the same as above described except that the high frequency oscillations are repeated for each half wave of the sup-' ply voltage.

In operation of the system shown in Fig. 4, upon impressing voltage on the system from the phases 38 to 40 of the three-phase supply circuit 31 through resistors 4 I to 43 thereby charging the capacitors to 51, the tubes 41 to 49 break down in turn and high frequency power is protil duced in the oscillating circuits 4 4 to 40. This power is taken out in the three separate circuits 60, GI, 62, inductively related respectively tothe inductors 52 to 54 of the oscillatory circuits.

Operation of the system shown in Fig. 5 is similar to that of Fig. 4 except that inFig. 5, wherein the oscillatory circuits 85 to 58 comprise the common inductor 59, the power is taken from theone output circuit I0 connected to the secondary II of the inductor 59.

In the systems of. Figs. 4 and 5. wherein the spacing of thetube electrodes50, 5| is relatively great, the, oscillations in any given tube in a half cycle persist for not more than 60 degrees of a half wave of the supply voltage as illustrated in Fig.- 6! The curves II3 to II! -are those of the supply voltage phases and curves I I to I I8 those of the corresponding high frequency oscillatory circuits. Therefore, in the circuit arrangements of Figs. 4 and 5, no phasing of the high frequency circuits is necessary 8 only; one tube can generate oscillations at a time.- However, -by proper adjustment of the tube electrode spacing the kilocycle frequency trains of oscillations IIB to IIO may be caused to overlap slightly or to allow a spacing of a few cycles between the successive oscillation periods as desired.

' In Fig. 7, operationv is similar to that above described in connection with Fig. 5 in, that high frequency power is produced in the three oscillatory circuits, to be taken oil in a single output circuit. In Fig. 'I, however, the coils of a phasing transformer 85 are so arranged that breakdown of any tube I5 to II introduces a positive voltage on another tube. The result is that all tubes having sufllcient voltage to break down do so at the same instant, or else do not break down until the succeeding cycle. For threephase operation. illustrated in Fig. '7, only two tubes pass current at a time but the currents overlap. Therefore, in the operation of the system of Fig. '7, a single phase high frequency output, in circuit 82 of Fig. '7 or circuit 09 of Fig. 8, is obtained from the three-phase input I circuit.

apply line current to the heater, whereupon movable element or bimetallic strip I06 moves the auxiliary electrode I04 into contact with the main electrode I00. Switch I08 is then opened thereby cutting off the heating current from heater I09. Current is now flowing in the starting electrode circuit through main electrode I00, auxiliary electrode I04 and resistance I07. As the strip I06 cools, because of the cutting off of 'heater current, the starting electrode I04, carried by the strip, moves .away from the main 1 electrode I00 and an arc is formed between electrodes I00 and I04. Current flow in the starting electrode circuit continues as the arc lengthens, and electrodes I00 and I04 are soon both incandescent. However, the are then shifts from electrode I04 to electrode IIII, thereby establishing a lower resistance return path, as current no longer need flow through the resistor WI. The system then starts operating, high frequency oscillations are produced in the oscillatory circult 96, and power is taken out in the output circuit I02.

My invention has been described herein in particular embodiments forpurposes of illustration. It is to be understood, however, that the invention-is susceptible of various changes and modifications and that by the appended claims I intend to cover any such modifications as fall within the true spirit and scope of my invention,

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric system comprising a relatively low voltage input circuit, an output circuit, and means to produce current of high frequency in said output circuit including an arc tube having two closely spaced similar electrodes in an inert gas under high pressure and an oscillation circuit in series with said are tube, said oscillation circuit including an inductor and a capacitor in series to determine the frequency of said output current. I

2. A high frequency power supply means comprising a relatively low voltage, low frequency alternating current supply circuit, an output circult, and means to supply oscillatory current to said output circuit including at least one arc tube having two closely spaced similar electrodes in an inert gas and an oscillation circuit in series with said are tube, said. oscillation circuit inseries to determine the frequency of said output current, said supply circuit, said arc tube, and said oscillation circuit being so connected and arranged that current from said supply circuit flows alternately in opposite directions through said arc tube.

3. An electric power supply means comprising an input circuit, a resistor, an oscillatory circuit including in series two are tubes and an inductor and a capacitor, means to connect one side of said input circuit to a lead connecting said tubes,

means to connect the other side of said input circuit through one section of said resistor to said inductor and one of said tubes, and means to connect said other side of said input circuit through another section of said resistor to said capacitor and the other of said tubes.

4. An electric power supply circuit comprising an input circuit, an oscillatory circuit including an inductor and a capacitor and arc tube apparatus having electrodes arranged to provide two space paths in series through said apparatus, means to connect one side of said input circuit to said tube apparatus at a point thereof between said paths, a resistance means connected across said oscillatory circuit and means to connect the other side of said input circuit to an intermediate point of said resistance means.

5. An electric power supply system comprising a polyphase alternating current input circuit, a plurality oi oscillatory circuits connected respectively to the corresponding phases of said input circuit and each including frequently determining means comprising capacitance and inductance, and a plurality of arc tubes associated respectively with the corresponding oscillatory circuits and each having a pair 01' electrodes, the spacing of said electrodes being such that oscillations in any given one of said oscillatory circuits persist 40 only until substantially the beginning of the oscillation period in the next succeeding one oi. said oscillatory circuits.

6. An electric power supply means comprising a three-phase alternating current input circuit, a

45 plurality of oscillatory circuits connected respectively to the corresponding phases of said input circuit and each including frequency determining means comprising capacitance and inductance,

and a plurality of arc tubes associated respec- 50 tively with the corresponding oscillatory circuits,

each of said tubes-including a pair of electrodes, the spacing of said electrodes being such as to prevent oscillations in any given one of said oscillatory circuits for more than substantially sixty degrees of a half wave of the corresponding phase 01' said input circuit. I" i 7. An electric power supply system comprising a polyphase alternating current input circuit, a plurality of oscillatory circuits connected respectively to the corresponding phases of said input circuit and each including a capacitor and an arc tube having a pair of electrodes, and a single inductor common to said oscillatory circuits, the spacing of said electrodes being such that oscillations in any given one of said oscillatory circuits persist only until substantially the beginning of the oscillation period in the next succeeding one oi said oscillatory circuits.

. 8. An electric power supply system comprising a three-phase alternating current input circuit, three oscillatory circuits connected respectively ,to the corresponding phases of said input circuit and each including a capacitor and an arc tube having a pair of electrodes, a single inductor common to said oscillatory circuits, the spacing 01' said electrodes being such as to prevent oscillations in any given one of said oscillatory circuits for more than substantially sixty degrees of a hall wave 01 the corresponding phase of said input circuit, and an output circuit associated with said inductor.

9. An electric power supply system comprising an input circuit, an output circuit, means to produce oscillatory current in said output circuit including an inductor, a capacitor, and'an arc tube having a pair oi. main electrodes and an auxiliary starting electrode, and circuit means to actuate said auxiliary electrode to initiate oscillations in said are tube, said circuit means including a resistance, a thermostatic device having a heater element' and a movable element in operative relation with said auxiliary electrode, and a switch means adapted when closed to supply heating current to said heater element from said input circuit to cause said auxiliary electrode to make contact with one of said main electrodes and when open to cause current from said input circuit to flow ,in series through said one of said main electrodes,

said auxiliary electrode, and said resistance.

.- LAWRENCE D. MILES. 

